One of the most common techniques for the controlled delivery of conditioned air (heated, cooled or both) to a plurality of rooms in a structure is to use a variable air volume (VAV), constant temperature system. The conditioned air from a central source is discharged into the various spaces or rooms through a plurality of diffusers located in the rooms. One common approach to the control of such air conditioning systems is to use a thermostat located in each room, which thermostat regulates a damper or control plate in the diffuser to modulate the volume of air discharged into the room, depending upon the temperature demand of the room as sensed by the room thermostat. U.S. Pat. Nos. 3,117,723, 3,824,800 and 4,238,071, for example, disclose room thermostat controlled air diffusers in which the thermostat controls the operation of a pneumatic actuator for the diffuser damper.
Thermally-powered diffuser damper assembly actuators also have been employed in connection with air conditioning systems. U.S. Pat. Nos. 3,732,799, 3,743,180, 4,123,001, 4,509,678, 4,537,347, 4,570,850 and 4,697,736 are all examples of the use of thermal sensor-actuators which have been used to drive damper assemblies in connection with air diffusers and ventilating systems. Such diffusers typically employ a sensor-actuator element (e.g., U.S. Pat. Nos. 2,932,454 and 3,442,078) of the type which has been widely used in the automobile industry in connection with the control of radiator relief valves.
Thermally-powered air diffusers have the advantage of essentially incorporating the thermal sensor function of a thermostat directly into the diffuser assembly itself. This avoids the necessity for wiring or other couplings between a room thermostat and the diffuser. Moreover, thermal sensor-actuators provide the power for operation of the diffuser damper assembly, which eliminates the need for supplying outside power to each diffuser. The result has been that such thermally-powered sensor-actuator diffusers inherently are less costly than conventional thermostat controlled systems.
Through the use of various combinations of thermal sensor-actuators and damper displacement linkages or drive assemblies, thermally-powered sensor-actuators can be used to control both heating and cooling of a space. U.S. Pat. Nos. Re. 30,953, 4,491,270 and 4,523,713, for example, disclose thermally-powered .sensor-actuator systems which are capable of cooling only, cooling with warm-up heating, and cooling and heating. The sensor-actuators are positioned so as to sense both the duct or supply air temperature and the room or secondary air temperature.
Secondary air temperature is particularly valuable in accurately controlling air diffuser operation. One of the functions in an air diffuser is to distribute air evenly along the ceiling of a room without undesirable dumping so that the conditioned air will entrain the room air so that a pattern of air circulation in the room will be established which is highly effective in mixing the conditioned air with the room air. The result that is desired is for the air circulating in the room to follow donut or toroidal paths and return backup to the diffuser. The secondary air returning to the diffuser will have a temperature which is very close to the average temperature of the room. Controlling diffuser operation based upon this average room temperature, rather than a temperature sensed along a wall, which is where most thermostats are located, results in better control of the conditioning of the room air.
One of the important considerations when using thermally-powered sensor-actuators to control diffuser operations is that the assembly or linkage which drives the diffuser damper blade assembly must not contain too much friction or undesirable hysterisis. Thus, close coupling or positioning of the sensor-actuators to the damper assembly which is to be driven is highly desirable.
While thermally-powered sensor-actuator driven diffuser systems are less expensive than conventional thermostat controlled diffusers, there are installations in which it would be highly desirable to be able to further reduce the cost of an air diffuser system. In most buildings, for example, the heating and cooling load in many rooms is essentially the same. Thus, it is quite possible and highly advantageous from the view point of costs to employ a master-slave or active terminal and passive satellite air diffuser system. In such systems, one of the diffusers is active or controlled, while the others are passive or merely follow or are slaved to the master. This approach has been employed extensively with conventional thermostat-controlled diffuser systems with attendant cost savings. Typical of the commercially available prior art active master terminal and passive satellite or slave terminals is the MODULINE air terminal system manufactured by Carrier Corporation and described in the Carrier product brochure entitle "Carrier Moduline Air Terminals." A similar system is manufactured by York and sold under the model designation Model ISCS. Master-satellite diffuser systems have not heretofore been employed in thermally powered systems. Further cost savings could be achieved, however, if a thermally-powered master-slave air diffuser system could be developed.
Accordingly, it is an object of the present invention to provide a thermally-powered active master and passive satellite air diffuser system having a high degree of responsiveness and accuracy in controlling the air discharged therefrom.
Another object of the present invention is to provide a thermally-powered master diffuser for use in a master-slave air diffuser system which can be packaged as a single unit for ease of installation and ease of coupling to slave units control operation of the slave units.
Still another object of the present invention is to provide a method for sensing and thermally powering a master-slave diffuser system which has enhanced precision of performance and is adaptable to a wide range of installations.
Still a further object of the present invention is to provide a thermally-powered, master-slave air diffuser system in which the driving of the flow control damper assembly is enhanced.
It is an object of the present invention to provide a thermally-powered, master-slave air diffuser apparatus and method which is easy to install, reliable in its operation, durable and requires little maintenance, and can be adjusted and adapted to a wide range of installations.
The thermally-powered, master-slave air diffuser system of the present invention has other objects and features of advantage which will become apparent from the accompanying drawings and are set forth in more detail in the following description of the Best Mode Of Carrying Out The Invention.